Where must the discharge of the regulator vent be when a container is installed underground?

The correct answer is that the discharge of the regulator vent must be placed above the highest probable water level when a container is installed underground. This requirement is crucial for safety and proper functioning of the gas system.

The reasoning behind this is that if the vent is located below the water level, it can become submerged in water during heavy rains or flooding. This situation may trap gas within the regulator or allow moisture to enter the system, potentially causing malfunctions or unsafe conditions. By ensuring that the vent is installed above this water level, it prevents water from interfering with the venting of gas, supporting effective ventilation and reducing risks of gas accumulation or pressure issues.

Setting the vent at ground level, below the frost line, or at a height of 3 feet above the ground does not guarantee that it will be safe from water intrusion, particularly in areas prone to flooding or high groundwater levels. Therefore, placing the vent above the highest probable water level is the most effective and prudent practice.